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What makes a “lightweight” desktop environment lightweight?

Over the last few days I was wondering what is a “lightweight” desktop. And I must say I couldn’t come up with an answer to that question.

I was considering various things like “being memory efficient” which I discarded for obvious reasons. First of all it’s difficult to measure memory usage correctly (I haven’t seen anyone, who provides numbers, doing it correctly, this includes especially Phoronix). And then it’s comparing mostly apples to oranges. Loading a high-resolution wallpaper might make all the difference in the memory usage. Also if desktop environment Foo provides features which are not provided by Bar it’s obvious that Foo uses more memory. But still it’s apples vs oranges. It’s not a comparison on memory, it’s a comparison of features. And of course one might consider the Time-memory-tradeoff.

So is it all about features? Obviously not. If there is a feature a user needs and uses it cannot be bloat. The fact that a desktop environment has only few features cannot be the key to being lightweight. Being evil now: many people say GNOME is removing features, but nobody would say that GNOME is lightweight.

What about support for old systems? That’s not lightweight, that’s support for old hardware. And it’s something which doesn’t make any sense given Moore’s law. Which raises the first question: what is old hardware? One year, two years, ten years? Is it a moving target or is a Pentium III for all time the reference? Optimizing for old hardware means not making use of modern hardware capabilities. But does that make sense to not use modern hardware if it is available? Using the GPU for things the GPU can do better than the CPU is a good thing, isn’t it? Parallelize a computation on multi-core if possible is a good thing, isn’t it? But if you do so, you are optimizing for modern hardware and not for old hardware. So saying you are good for old hardware, implies you are bad on new hardware? Also I’m wondering how one can optimize for old hardware? Developers tend to have new hardware to not have problems like this. And how can one keep support for old hardware when the complete stack is moving towards new hardware? Who tests the kernel against old hardware? Who provides DRI drivers for obsoleted hardware which doesn’t fit into modern mainboards (who remembers AGP or PCI)? Who ensures that software is still working on 32 bit systems, who would notice such a breakage for example in the X-Server? So lightweight cannot be fit for old hardware. And remember: optimizing for old hardware is not the same as optimizing for modern low-end hardware. Even the Raspberry Pi has a stronger CPU (700 MHz) than the oldest Pentium III (450 MHz) – not to mention things like OpenGL…

What’s it then? Let’s ask Wikipedia. For Xfce it tells us, that “it aims to be fast and lightweight, while still being visually appealing and easy to use”. Unfortunately there’s no link on lightweight and also no reference. Let’s try again, LXDE: “The goal of the project is to provide a desktop environment that is fast and energy efficient”. Again no real definition and just stating a goal. But it goes on:

LXDE is designed to work well with computers on the low end of the performance spectrum such as older resource-constrained machines, new generation netbooks, and other small computers, especially those with low amounts of RAM.

I have no idea what a “new generation netbook” is, but it sounds like something modern half a decade ago. But we are down to the “being good on old hardware”, which we just discarded. Interestingly Wikipedia has references to prove that LXDE is good on RAM – unfortunately it’s references to Phoronix. Shame on you, Wikipedia, that’s a “benchmark” which has been considered seriously flawed by people understanding the topic.

Ok Phoronix aside, there is one more of the lightweight desktops to check. Razor-qt: “is a lightweight, Qt-based free software desktop environment for the X Window System. Unlike the KDE desktop environment which is also based on Qt, Razor-qt usually performs well even when used in computers with older hardware”. Damn, it again only claims and no reference for anything. Who says that KDE desktop environment (what’s that again?) is not performing well on older hardware? And what does the “usually” mean in that sentence?

So all Wikipedia gives us, is buzzword bingo and various claims without any proof (and not even a “reference missing”). Let’s try different and go to the projects directly.

Xfce tells us that it “is a lightweight desktop environment for UNIX-like operating systems. It aims to be fast and low on system resources, while still being visually appealing and user friendly.” Which sounds very similar to what Wikipedia wrote. Unfortunately nothing that tells us what lightweight means or what fast is or low on system resources. Fuzzy is fuzzy.

LXDE also has the same definition as shown in Wikipedia (maybe we should mark those wiki articles as advertisement?) but at least gives us a definition for what lightweight means to them: “It needs less CPU and performs extremely well with reasonable memory.” Fuzzy is fuzzy. What’s “reasonable memory” and “less CPU”? It goes on about various other things like “fast” and “energy saving” (which even are contradicting, e.g. fast is defined as working on hardware from 1999 and not require 3D – how that can be energy saving on new hardware one has to show me). The point energy saving is quite funny as it just says they are better than “other systems”. Oh well fuzzy is fuzzy.

Last but not least: Razor-qt. Razor doesn’t say it’s lightweight:

Razor-qt is an advanced, easy-to-use, and fast desktop environment based on Qt technologies. It has been tailored for users who value simplicity, speed, and an intuitive interface. Unlike most desktop environments, Razor-qt also works fine with weak machines.

Fuzzy is fuzzy. What’s a “weak machine”, what are the “most desktop environments”? Where’s the proof for other DEs not working well on those not-defined “weak machines”?

And here, poor fool! with all my lore I stand, no wiser than before. All what I could derive from studying what lightweight means is, that one just has to claim to be lightweight. Bonus points if you include it into your name. It seems like if you repeat it often enough people will repeat it and it will turn out into truth.

First and foremost, lightweight is a comparison. Is your WM lighter on cpu and RAM than X% of other WMs? Faster? Then it's lightweight.

Yet it's inherently a fuzzy term, as it focuses on user experience, with varying old hardware, bad drivers, and so on. What percentage does one pick, and what metric? (count alone, market share, installed base...)

There may be no clear, well-defined term, but everyone agrees that KDE is heavy

Single most important criteria for light weight should be the number of CPU wakeups the desktop processes cause. For example, E17 is NOT a lightweight DE because on my laptop, it will last 4.5hours while KDE will last 6hours on full charge (both use whatever desktop effects they support for Intel 4000). That's a huge difference!

Single most important criteria for light weight should be the number of CPU wakeups the desktop processes cause. For example, E17 is NOT a lightweight DE because on my laptop, it will last 4.5hours while KDE will last 6hours on full charge (both use whatever desktop effects they support for Intel 4000). That's a huge difference!

That is a big difference, but now you've added a whole new metric to the equation.